We will continue to evaluate the role of steroid profile and thyroid hormone profile monitoring in optimizing both diagnosis and treatment of different endocrine diseases. We developed a state of the art micro assay for 11 steroids by LCMSMS. This assay has been used to optimize the treatment of patients with CAH (Dr Merke, collaborator). We have also shown that there is a statistically significant diurnal fluctuation in steroid concentrations for all steroids tested except progesterone. The extent of this diurnal variation is so large that it clearly necessitates development of new time dependent reference intervals. Manuscript published in Clinical Chemistry and J Steroid Biochem Mol Biol. We will also examine the role of our new free steroid profile and free 25 OH Vitamin D3 assays in health and disease. We have also measured thyroid hormone concentrations, choline and neurosteroid concentrations throughout pregnancy. The work described above has been published in numerous papers, a few of which are listed below.